1. Field of the Invention
The present invention relates to composite particles and a production process thereof, as well as to an aqueous dispersion containing the composite particles and water, to an aqueous dispersion composition for chemical mechanical polishing (hereunder referred to as xe2x80x9cCMP slurryxe2x80x9d), and to a process for manufacture of semiconductor device.
The composite particles of the invention have improved strength and hardness, excellent heat resistance, and can be utilized as cosmetics, electronic materials, magnetic materials, coating materials, paints, spacers, optical materials, catalysts, photocatalysts, fillers, electronic material film lubricants, diagnostic agents, drugs, conductive materials, sensor materials, toners, resin modifiers, inks, adsorbing agents, ultraviolet-resistant materials, and masking materials, for example, and may be in the form of an aqueous dispersion to be used as a polishing material for magnetic disks or wafers. The CMP slurry of the present invention can also be suitably used for manufacture of various semiconductor device.
2. Description of the Background
Polymer particles have conventionally been used for standard particles, diagnostic agent carrier particles, and lubricants, for example with a narrow particle size distribution obtained by copolymerizing vinyl monomers or the like. However, such polymer particles do not always exhibit sufficient strength and heat resistance, and when used as standard particles or lubricants, application of excess shear stress or exposure to high temperature can cause deformation or destruction of the particles, and therefore their uses are limited. In order to address these problems there have been proposed particles made of copolymers of crosslinkable vinyl monomers, for example, that are copolymerized with a high degree of crosslinking. However, particles made of such crosslinked polymers have lower hardness and insufficient heat resistance compared to inorganic-based particles, and therefore are not suitable for a very wide range of uses.
For uses such as electronic materials, magnetic materials, and heat-resistant materials, for example, there have been employed particles made of numerous metal compounds, and a variety of composite particles have been proposed for diverse purposes. As such types of composite particles there may be mentioned composite particles comprising iron oxide particles coated with silicon compounds, so that in production of filamentous magnetic bodies by heat treatment it is possible to prevent shape collapsing and sintering between magnetic bodies; composite particles comprising iron powder coated with copper as a high strength material for powder metallurgy; and composite particles comprising iron oxide particles coated with antimony oxide and aluminum oxide for improved heat resistance. However, since such composite particles are all composed of metal compounds, they are too hard and are not always adequately suited for diverse purposes. The development of composite particles with appropriate hardness has thus become a necessity particularly in the fields of electronic materials, magnetic materials, optical materials, polishing materials, and so forth.
Aqueous dispersions of oxide particles such as colloidal silica or colloidal alumina have been commonly used as polishing materials for chemical mechanical polishing of semiconductor element surfaces and semiconductor element interlayer insulating films in semiconductor devicees, and particularly as polishing materials for wafer surfaces. However, aqueous dispersions of such oxide particles tend to form aggregates due to their low dispersion stability, and the aggregates create surface defects (hereunder referred to as xe2x80x9cscratchesxe2x80x9d) in polishing surfaces, that result in reduced yields of the semiconductor products. As a method of addressing this problem there have been proposed a method of adding surfactants to oxide particle dispersions, a method of using homogenizers or the like for more even dispersion, and a method of removing the aggregates with filters. However, these measures not only fail to improve the polishing materials themselves, but can also create new problems, such as lower polishing rates and contamination of polishing surfaces by metal ions.
Japanese Laid-open Patent Publication No. Hei-7-86216 discloses a process for production of a semiconductor device by chemical mechanical polishing using particles made of an organic polymer compound. In this process, the residual polishing particles can be fired and removed after polishing, to thus avoid imperfections in semiconductor devicees by those residual particles. Nevertheless, since the particles made of this organic polymer compound have lower hardness than silica or alumina particles, it has not been possible to achieve high polishing rates therewith.
Accordingly, it is an object of the present invention to provide composite particles that exhibit adequate strength and hardness, excellent heat resistance, and suitable flexibility by providing metal compound sections in the interior and on the surface of the polymer particles, thus allowing their use for the wide range of purposes mentioned above, as well as a production process thereof.
It is another object of the present invention to provide an aqueous dispersion containing these composite particles and water, which is useful for a variety of purposes such as electronic materials, magnetic materials, optical materials, and the like, and particularly an aqueous dispersion to be used for polishing of magnetic disks.
It is still another object of the present invention to provide a CMP slurry wherein a silicon compound section or metal compound section is provided in the polymer particles to give the surface thereof adequate strength and hardness, excellent heat resistance and suitable flexibility and to increase the polishing rate while also preventing scratches, and by providing a process for manufacture of semiconductor devices using the CMP slurry. The CMP slurry is useful for chemical mechanical polishing in the manufacture of semiconductor devicees, and especially chemical mechanical polishing of wafer surfaces.
The composite particles of the present invention are characterized by having polymer particles and at least one of a metal compound portion or section which is at least one of a metalloxane bond-containing section and a metal oxide particle section, provided that titanium is not the metal of the metalloxane bond-containing section, and a silica particle portion or section formed directly or indirectly on the polymer particles.
The production process for the composite particles of the present invention is characterized by chemically bonding part of a coupling compound to polymer particles and then at least one of (1) chemically bonding or chemically bonding and polycondensing a compound of {circle around (1)} described below and (2) chemically bonding a compound of {circle around (2)} described below to another part of the coupling compound to form at least one of a metal compound section and a silica particle section indirectly on the polymer particles.
{circle around (1)} A compound having the formula RnM(ORxe2x80x2)z-n (Compound {circle around (1)} and {circle around (2)} are: where R is a monovalent organic group of 1-8 carbon atoms, Rxe2x80x2 is an alkyl group of 1-5 carbon atoms, an acyl group of 2-6 carbon atoms or an aryl group of 6-9 carbon atoms; M is Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, Zr, Nb, Mo, Sn, Sb, Ta, W, Pb or Ce; and z is the valency of M. Also, n is an integer of 0 to (zxe2x88x921), and when n is 2 or greater, each R may be the same or different. When (zxe2x88x92n) is 2 or greater, each Rxe2x80x2 may be the same or different.
{circle around (2)} At least one compound from among colloidal alumina, colloidal titania, colloidal zirconia, colloidal ceria and colloidal silica.
Further, the production process for the composite particles according to the present invention is characterized by at least one of (1) chemically bonding or chemically bonding and polycondensing the compound of {circle around (1)} and (2) chemically bonding the compound of {circle around (2)} to polymer particles in the presence of the polymer particles, to form at least one of a metal compound section and a silica particle section directly on the polymer particles, without using the coupling compound used for the present invention.
The aqueous dispersion of the present invention contains water and composite particles having polymer particles and at least one of a metal compound portion or section (at least one of a metalloxane bond-containing section and a metal oxide particle section, provided that titanium is not the metal of the metalloxane bond-containing section) and a silica particle portion or section formed directly or indirectly on the polymer particles.
The CMP slurry of the present invention contains water and composite particles having polymer particles and at least one of a silicon compound portion or section and a metal compound portion or section formed directly or indirectly on the polymer particles.
The CMP slurry according to another aspect of the present invention contains water and composite particles obtained by chemically bonding part of a coupling compound to polymer particles and then at least one of (1) chemically bonding or chemically bonding and polycondensing a compound of {circle around (1)} and (2) chemically bonding a compound of {circle around (2)} to another part of the coupling compound, to form at least one of a silicon compound section and a metal compound section indirectly on the polymer particles.
Further, the CMP slurry according to another aspect of the present invention is characterized by containing water and composite particles obtained by at least one of (1) chemically bonding or chemically bonding and polycondensing the compound of {circle around (1)} and (2) chemically bonding the compound of {circle around (2)} in the presence of polymer particles, to form at least one of a silicon compound section and a metal compound section directly on the polymer particles.
The process for manufacture of a semiconductor device according to the present invention is characterized in that a CMP slurry containing water and composite particles having polymer particles and at least one of a silicon compound section and a metal compound section formed directly or indirectly on the polymer particles, is used for manufacture of a semiconductor device.
The process for manufacture of a semiconductor device according to another invention is characterized in that a CMP slurry containing water and composite particles obtained by chemically bonding part of a coupling compound to polymer particles and then at least one of (1) chemically bonding or chemically bonding and polycondensing a compound of {circle around (1)} and (2) chemically bonding a compound of {circle around (2)} to another part of the coupling compound, to form at least one of a silicon compound section and a metal compound section indirectly on the polymer particles, is used for manufacture of a semiconductor device.
Further, the process for manufacture of a semiconductor device according to another invention is characterized in that an aqueous dispersion composition for chemical mechanical polishing containing water and composite particles obtained by at least one of (1) chemically bonding or chemically bonding and polycondensing a compound of {circle around (1)} and (2) chemically bonding a compound of {circle around (2)} to polymer particles in the presence of the polymer particles, to form at least one of a silicon compound section and a metal compound section directly on the polymer particles, is used for manufacture of a semiconductor device.
The composite particles of the present invention have improved strength and hardness and excellent heat resistance, and are useful for various different purposes such as electronic materials, magnetic materials, optical materials, polishing materials and the like. The production process of the present invention can easily produce specific composite particles according to the present invention. In particular, another of the present inventions allows the same specific composite particles to be produced without using a coupling compound. Further, the aqueous dispersion of the present invention is useful for various different purposes including electronic materials, magnetic materials, optical materials and the like. The aqueous dispersion is particularly useful as a polishing material for magnetic disks and wafers.
The CMP slurry of the present invention has improved and, thus, adequate strength and hardness, excellent heat resistance, and provides a sufficiently high polishing rate, while offering excellent polishing performance that produces no scratches on polishing surfaces. The CMP slurry of the present invention is also useful for chemical mechanical polishing in the manufacture of semiconductor devices, and particularly for polishing of wafer surfaces.
The process for manufacture of semiconductor devices according to the present invention also allows easy and convenient manufacture of high-quality semiconductor devices.
The present xe2x80x9cpolymer particlesxe2x80x9d are particles composed of a polymer obtained by polymerization of various different monomers. The monomers used may be unsaturated aromatic compounds such as styrene, xcex1-methylstyrene, halogenated styrene and divinylbenzene; unsaturated esters such as vinyl acetate and vinyl propionate; or unsaturated nitriles such as acrylonitrile. There may also be used acrylic acid esters or methacrylic acid esters, such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, ethyleneglycol diacrylate, ethyleneglycol dimethacrylate, glycidyl acrylate, glycidyl methacrylate, 2-hydroxyethyl acrylate, acryl acrylate and allyl methacrylate.
There may also be used butadiene, isoprene, acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, and the like. These monomers may be used alone or in combinations of two or more. The monomers may also have functional groups introduced therein, such as hydroxyl groups, epoxy groups, carboxyl groups and the like. When such functional groups are introduced into the polymer particles, it is possible to form a metal compound section or silica particle section directly on the polymer particles without requiring a coupling compound such as a silane coupling agent. However, if the silane coupling agent used has functional groups that can react with the introduced functional groups, bonding between the metal compound section or silica particle section and the polymer particles can be further accelerated, thus yielding composite particles with even better performance.
The polymer particles can be obtained by polymerization of the monomers by any of various processes such as emulsion polymerization, suspension polymerization and dispersion polymerization. These polymerization processes allow appropriate adjustment of the particle size of the polymer particles based on the polymerization conditions. Bulk polymers and the like can be pulverized to obtain polymer particles of a prescribed particle size. When polymer particles with particularly high strength and excellent heat resistance are required, polyfunctional monomers may be used together during production of the polymer particles to introduce a crosslinked structure into the molecule. The crosslinked structure can be introduced by a method such as chemical crosslinking or electron beam crosslinking either during production of the polymer particles, or after production of the polymer particles.
The polymer particles used may be particles composed of various different monomers, such as polyamides, polyesters, polycarbonates and polyolefins, in addition to those mentioned above, and these polymer particles may also have functional groups introduced therein in the same manner as described above, as well as crosslinked structures introduced into the molecules.
The shape of the polymer particles is not particularly restricted, but they are preferably as spherical as possible. The mean particle size as measured with a LASER PARTICLE ANALYZER PAR-III (product of Otsuka Electronics, CO. LTD.) is preferably 0.02-50 xcexcm, especially 0.05-20 xcexcm, and more preferably 0.05-1.0 xcexcm. If the mean particle size is smaller than 0.02 xcexcm the particles will tend to aggregate, and if it exceeds 50 xcexcm the dispersion stability will be undesirably impaired when an aqueous dispersion is prepared.
At least part of the xe2x80x9cmetal compound sectionxe2x80x9d and xe2x80x9csilica particle sectionxe2x80x9d of the composite particles of the present invention is chemically or non-chemically bonded to the polymer particles either directly or indirectly, but xe2x80x9cchemically bondingxe2x80x9d is particularly preferred. This avoids a problem whereby they easily shed from the polymer particles. The chemical bonding may be covalent bonding, ionic bonding or coordination bonding, but covalent bonding is preferred for a stronger bond. As non-chemical bonding there may be mentioned hydrogen bonding, surface charge bonding, interlocking bonding and anchor effect bonding.
Further, the xe2x80x9cmetal oxide particle portion or sectionxe2x80x9d may consist of an xe2x80x9calumina particle sectionxe2x80x9d, xe2x80x9ctitanic particle sectionxe2x80x9d or xe2x80x9czirconia particle sectionxe2x80x9d, or it may be composed of all of these. The alumina particle section, titanic particle section and zirconia particle section, as well as the silica particle section, may be formed in the interior or on the entire surface of the polymer particles, or they may be formed on a part thereof. The xe2x80x9cmetalloxane bond-containing portion or sectionxe2x80x9d may consist of a single molecule, but is preferably a coupled structure of two or more molecules. In the case of a coupled structure, it may be linear but is more preferably a two-dimensional or three-dimensional structure.
In the CMP slurry of the present invention, at least part of the xe2x80x9csilicon compound portion or sectionxe2x80x9d and the xe2x80x9cmetal compound portion or sectionxe2x80x9d (hereunder referred to collectively as xe2x80x9ccompound sectionsxe2x80x9d) is chemically or non-chemically bonded to the polymer particles either directly or indirectly, but xe2x80x9cchemical bondingxe2x80x9d is particularly preferred. This avoids a problem whereby they easily shed from the polymer particles during polishing, thus remaining on the polishing surface. The chemical bonding may be ionic bonding or coordination bonding, but covalent bonding is preferred for a stronger bond. As non-chemical bonding there may be mentioned hydrogen bonding, surface charge bonding, interlocking bonding and anchor effect bonding.
Further, the silicon compound section may consist of a xe2x80x9csiloxane bond-containing sectionxe2x80x9d or a xe2x80x9csilica particle sectionxe2x80x9d, or it may be composed of both. The metal compound section may be consist of a xe2x80x9cmetalloxane bond-containing sectionxe2x80x9d, xe2x80x9calumina particle sectionxe2x80x9d, xe2x80x9ctitania particle sectionxe2x80x9d or xe2x80x9czirconia particle sectionxe2x80x9d, or it may be composed of two or more of these.
The siloxane bond-containing portion or section and silica particle portion or section, as well as the metalloxane bond-containing section, alumina particle section, titania particle section and zirconia particle section, may be formed in the interior or on the entire surface of the polymer particles, or they may be formed on a part thereof. The siloxane bond-containing section and metalloxane bond-containing section may consist of a single molecule, but is preferably a coupled structure of two or more molecules. In the case of a coupled structure, it may be linear but is more preferably a three-dimensional structure.
According to the present invention, each of the bond-containing sections and particle sections may be formed in the manner described above, or they may have the following structures.
(1) All of the bond-containing sections and particle sections may be directly or indirectly bonded either chemically or non-chemically to the polymer particles, or any one or more thereof may be bonded to the polymer particles.
(2) Another molecule may be bonded at the middle or end portions of the bond-containing sections or particle sections bonded to the polymer particles.
(3) The bond-containing sections or particle sections that are not bonded to the polymer particles and are also not bonded to the bond-containing sections or particle sections bonded to the polymer particles may be sequestered by the bond-containing sections or particle sections chemically or non-chemically bonded to the polymer particles.
The metal compound section or silica particle section may be formed by direct bonding to the polymer particles, or they may be formed by bonding through a coupling compound such as a silane coupling agent. In the latter case, the above-mentioned xe2x80x9ccoupling compoundxe2x80x9d is used which lies between the polymer particles and at least one of the compound of {circle around (1)} and compound of {circle around (2)}, and couples the polymer particles with at least one of the compound of {circle around (1)} and compound of {circle around (2)}. As coupling compounds there may be used coupling agents such as silane coupling agents, aluminum-based coupling agents, titanium-based coupling agents and zirconium-based coupling agents, but silane coupling agents are particularly preferred. The following listed as (a), (b) and (c) may be mentioned as silane coupling agents.
(a) vinyltrichlorsilane, vinyltris(xcex2-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, xcex3-methacryloxypropyltrimethoxysilane, xcex3-mercaptopropyltrimethoxysilane and xcex3-chloropropyltrimethoxysilane;
(b) xcex3-glycidoxypropyltrimethoxysilane and xcex3-glycidoxypropylmethyldiethoxysilane;
(c) N-xcex2(aminoethyl) xcex3-aminopropyltrimethoxysilane, N-(xcex2(aminoethyl) xcex3-aminopropylmethyldimethoxysilane and xcex3-aminopropyltriethoxysilane.
These silane coupling agents preferably have functional groups in the molecules that can easily react with the functional groups such as hydroxyl groups, epoxy groups and carboxyl groups introduced into the polymer particles. For example, for polymer particles having carboxyl groups introduced therein, the silane coupling agents of (b) and (c) above with epoxy groups and amino groups are preferred. Among these, xcex3-glycidoxypropyltrimethoxysilane and N-(xcex2(aminoethyl) xcex3-aminopropyltrimethoxysilane are particularly preferred.
As aluminum-based coupling agents there may be mentioned acetoalkoxyaluminum diisopropylate and the like, and as titanium-based coupling agents there may be mentioned isopropyl triisostearoyltitanate, isopropyltridecyl benzenesulfonyltitanate, and the like. These different coupling agents may be used alone or in combinations of two or more. Coupling agents of different types may also be used together.
The amount of coupling agent used between the polymer particles and the compound of {circle around (1)} or the colloidal substance of {circle around (2)} is preferably 0.1-50 moles with respect to one mole of the functional group belonging to or introduced into the polymer particles. The amount is more preferably 0.5-30 moles, and especially 1.0-20 moles. The amount of coupling agent used is less than 0.1 mole because the metal compound sections or particle sections will not bond with sufficient strength to the polymer particles, and will shed more easily from the polymer particles. If the amount used exceeds 50 moles, condensation reaction of the coupling agent molecules will be promoted, forming new polymers in addition to reaction with the molecules composing the polymer particles, and thus inhibiting bonding of the compound sections to the polymer particles. When the coupling agent is chemically bonded to the polymer particles, a catalyst such as an acid or base may be used to accelerate the reaction. The reaction system may also be heated to accelerate the reaction.
In the compound represented by the formula RnM(ORxe2x80x2)z-n above, M is Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, Zr, Nb, Mo, Sn, Sb, Ta, W, Pb or Ce, and z is the valency of M. As the R portion of the general formula there may be mentioned monovalent organic groups including alkyl groups such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, secbutyl, tert-butyl and n-pentyl groups, and phenyl, vinyl and glycidopropyl groups. As the Rxe2x80x2 portion there may be mentioned alkyl groups such as methyl, ethyl, n-propyl and iso-propyl groups, acyl groups such as acetyl, propionyl, butyryl, valeryl and caproyl groups, and aryl groups such as phenyl and tolyl groups, while n is an integer of 1 to (zxe2x88x922). In the case of two or more R and Rxe2x80x2 groups, they may be the same or different.
Particularly preferred as the M portion are Al and Zr, and these elements will be used for M in the following explanation.
As a compound where M is Al there may be mentioned aluminum ethoxide, and as a compound where M is Zr there may be mentioned zirconium tert-butoxide. These compounds induce formation of metalloxane bond-containing sections and alumina particle sections or zirconia particle sections. The compounds may be used alone or in combinations of two or more. Compounds where M is Al or Zr may also be used together. The value of (zxe2x88x92n) is 1 or greater, preferably 2 or greater and more preferably 3 or greater, in which case a more dense metalloxane bond-containing section is formed.
These compounds include not only those represented by the above general formula, but also either hydrolysates or partial condensates of the compounds. The compounds of the above general formula undergo hydrolysis or partial condensation without any special procedures, but if necessary a prescribed proportion thereof may be hydrolyzed or partially condensed beforehand.
These compounds are preferably used in a weight ratio of 0.001-100 with respect to the polymer particles, in terms of SiO2, Al2O3, TiO2 or ZrO2. The weight ratio is more preferably 0.005-50, and especially 0.01-10. If the weight ratio is under 0.001 the metal compound section will not adequately form in the interior and on the surface of the polymer particles. On the other hand, the weight ratio is above 100 since this will cause the hardness of the polymer particles to be too high.
The xe2x80x9ccolloidal aluminaxe2x80x9d, xe2x80x9ccolloidal titaniaxe2x80x9d, xe2x80x9ccolloidal zirconiaxe2x80x9d and xe2x80x9ccolloidal silicaxe2x80x9d consist of fine particles of alumina, titania, zirconia or silica with a mean particle size of 5-500 nm dispersed in a medium such as water. The fine particles may be prepared by particle growth in an aqueous alkali solution, by polycondensation of a metal alkoxide or by a gas phase method, and in practice they are used as colloids dispersed in a medium such as water. Colloidal titania and colloidal silica can be produced from compounds of the general formula RnM(ORxe2x80x2)z-n where M is Ti or Si, similar to colloidal alumina and colloidal zirconia, and a titania particle section and silica particle section can also be formed thereby.
The fine particles can be constructed with an alumina particle section, titania particle section, zirconia particle section or silica particle section without any bonding with the polymer particles. In such cases, however, they must be sequestered with a metalloxane bond-containing section or the like. They may also be bonded with the polymer particles or with the metalloxane bond-containing section by the hydroxyl groups formed in the fine particles, to construct the particle sections. The amount of colloid used is preferably in a weight ratio of 0.001-100 with respect to the polymer particles, in terms of Al2O3, TiO2, ZrO2 or SiO2. The weight ratio is more preferably 0.01-50, and especially 0.1-10. When the weight ratio is less than 0.001, the particle sections will be insufficiently formed. It is also preferably not over 100 since the hardness of the polymer particles will become too high.
The bonding of each coupling agent to the polymer particles and the reaction of the compound of {circle around (1)} and the colloidal alumina, and the like. of {circle around (2)} with each coupling agent, or their direct reaction with the polymer particles, can be accomplished in dispersion systems where organic solvents such as water or an alcohol are used as the dispersion media. These dispersion media may be of a single type, or they may be a combination of two or more appropriate dispersion media such as water and alcohol. When water is included in the dispersion medium, it is preferred to introduce hydrophilic functional groups such as hydroxyl groups, epoxy groups or carboxylic groups into the polymer particles in order to stabilize the polymer particles in the dispersion system and achieve uniform dispersion. Introduction of these functional groups can also promote easier chemical bonding and/or non-chemical bonding of the coupling agents or the compound of {circle around (1)} and the compound of {circle around (2)} with the polymer particles.
Preferred alcohols for use include lower saturated aliphatic alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol and the like. These alcohols can be used alone or in combinations of two or more. Other organic solvents besides alcohol, such as methyl ethyl ketone and dimethylformamide may be used, and these organic solvents, water and alcohol may also be used in combination in appropriate weight ratios.
In this reaction, the polymer particle content in the dispersion medium is preferably 0.001-70 wt % (hereunder all xe2x80x9cvalues will mean xe2x80x9cwt %xe2x80x9d), more preferably 0.01-50%, and especially 0.1-25%. If the content is under 0.001% the composite particle yield will be low, and if it is over 70% the dispersion stability of the polymer particles will be reduced, tending to cause gelling at the compounding stage.
Further, the reaction for formation of the metal compound section or silica particle section can be promoted by heating or using a catalyst. For heating, the reaction system temperature is preferably 40-100xc2x0 C. As catalysts there may be used acids, bases, aluminum compounds, tin compounds and the like. Acid catalysts and aluminum catalysts provide a particularly notable effect of promoting the reaction. In this production process, the metal compound section is preferably formed first, after which the dispersion is diluted with water or an alkaline aqueous solution, and if necessary the alcohol or other organic solvent is then removed using an evaporator or the like.
The dilution may be carried out using water or an alkaline aqueous solution such as an aqueous solution of ammonia or an aqueous solution of potassium hydroxide. The concentration of the alkaline aqueous solution is preferably 0.001-10%, and especially 0.01-1%. The dilution procedure preferably involves dropwise addition of the dispersion containing the composite particles to the diluting agent using a dispenser, pipette or the like, but the water or alkaline aqueous solution may also be added while stirring the dispersion containing the composite particles.
The shape of the xe2x80x9ccomposite particlesxe2x80x9d is not particularly restricted but is preferably as spherical as possible. The mean particle size (sphere-equivalent size) is preferably 0.03-100 xcexcm, more preferably 0.05-20 xcexcm, and especially 0.05-1.0 xcexcm. If the mean particle size is less than 0.03 xcexcm the particles will be too small, failing to give the properties required for such uses as electronic materials, magnetic materials, optical materials, polishing materials, and the like., while if the mean particle size is greater than 100 xcexcm the shelf-life of aqueous or other dispersions containing the composite particles will be notably shortened. The mean particle size of the composite particles may be measured with the same type of device as for the polymer particles.
The composite particles can be used as a polishing material. The polishing material may contain the composite particles alone, or the polishing material may have an acid, alkali, oxidizing agent and/or surfactant added thereto.
The aqueous dispersion containing the composite particles and water can be applied for a variety of different uses. The aqueous dispersion may also contain other desired components such as acids, oxidizing agents and the like if necessary, and can be used as a polishing material for magnetic disks, and the like. The content of the composite particles in the aqueous dispersion is preferably 0.001-70%. The content is more preferably 0.01-50%, and especially 0.1-20%. If the content of the composite particles is less than 0.001% the performance required for such uses as electronic materials, magnetic materials, optical materials, polishing materials, and the like. will not be obtained, while if it is greater than 70% the shelf-life of the aqueous dispersion containing the composite particles will be notably shortened. The medium of the aqueous dispersion may be water alone, or it may be a mixed medium containing an organic solvent such as an alcohol in combination therewith, so long as the polymer particles do not dissolve.
The composite particles are useful for chemical mechanical polishing, and especially wafer surface polishing, employed in the manufacture of semiconductor devicees or devices, and the composite particles may be combined with water as an aqueous dispersion to be used as a polishing material for manufacture of semiconductor devices (wafers, and the like.). In addition to aqueous dispersions, they may also be in the form of a CMP slurry using an appropriate organic solvent medium that does not dissolve the polymer particles, such as an alcohol dispersion. In the case of a CMP slurry, the composite particle content is preferably 0.001-70%. The composite particle content is more preferably 0.01-50%, and especially 0.1-20%. If the content is less than 0.001%, the required polishing performance cannot be obtained, and if it exceeds 70%, the shelf-life of the CMP slurry containing the composite particles will be notably shortened.
According to the present invention, the aqueous dispersion or CMP slurry may also contain, if necessary, various other additives in addition to the surfactant (for example, oxidizing agents, chelating agents, organic acids, surfactants, pH regulators, and the like.). Such addition can increase the polishing rate, stabilize the oxidizing agent, allow more even dispersion of the polymer particles, and adjust for differences in the polishing rate when polishing films of different hardness, as in cases where two or more working films are polished.
Inclusion of potassium hydroxide or ammonia allows polishing of insulating films, and inclusion of tungsten, aluminum, copper and the like allows polishing of metal films. The composition (particularly a CMP slurry) can also be used in combination with another composition (especially a CMP slurry) in an appropriate weight ratio.
The xe2x80x9coxidizing agentxe2x80x9d used is not particularly restricted so long as it is water-soluble, and it is preferably selected as appropriate depending on the electrochemical properties of the metal layer of the working film of the wafer, based on a Pourbaix diagram, for example.
As specific oxidizing agents there may be mentioned organic peroxides such as hydrogen peroxide, peracetic acid, perbenzoic acid, tert-butylhydroperoxide, and the like; permanganate compounds such as potassium permanganate, and the like; bichromate compounds such as potassium bichromate, and the like; halogenate compounds such as potassium iodate, and the like; perhalogenate compounds such as perchloric acid, and the like; transition metal salts such as potassium ferricyanide, and the like; persulfuric compounds such as ammonium persulfate, and the like; polyvalent metal salts such as iron nitrate, cerium ammonium nitrate, and the like; and heteropoly acids such as silicotungstic acid, phosphotungstic acid, silicomolybdic acid, phosphomolybdic acid, and the like. Two or more of these may also be used in combination. By including such oxidizing agents it is possible to vastly increase the polishing rate for polishing of metal layers, and particularly of working films of wafers.
The oxidizing agent content may be 0.1-15 parts, and is particularly preferred to be 0.3-10 parts and especially 0.5-8 parts, with respect to 100 parts of the aqueous dispersion composition. If the content is less than 0.1 part the polishing rate of the aqueous dispersion composition will not be sufficiently increased. On the other hand, a sufficient improvement in the polishing rate can be achieved with a content of 15 parts, so that there is no need to include it at greater than 15 parts.
Examples of the xe2x80x9cchelating agentxe2x80x9d may be used with no particular restrictions so long as they can form metal chelate compounds, when the wafer working surface film is a metal. When the metal is copper, a compound containing nitrogen is particularly preferred.
As examples there may be mentioned triazole, indole, benzimidazole, benzotriazole, benzoxazole-benzotriazole, quinoline, quinolinic acid, quinoxaline, benzoquinoline, benzoxidine, ammonia, ethylenediamine, triethanolamine, glycine, alanine, leucine, glutamine, glutamic acid, tryptophan, 5-amino-1H-tetrazole, 7-hydroxy-5-methyl-1,3,4-triazaindolazine, benzoguanamine, salicylaldoxime, adenine, guanine, phthalazine, 5-methyl-1H-benzotriazole, 4-amino-1,2,4-triazole, and the like.
By adding appropriate amounts of these chelating agents it is possible to increase the polishing rate for polishing of the metal layers of wafers in particular, and thus improve the planarizing characteristics thereof. These chelating agents can also be used in combinations of two or more. The amount of the chelating agent added may be 0.01-5 parts, preferably 0.02-2 parts and especially 0.04-1 part, with respect to 100 parts of the aqueous dispersion composition.
The xe2x80x9corganic acidxe2x80x9d can further improve the polishing rate. As organic acids there may be mentioned para-toluenesulfonic acid, dodecylbenzenesulfonic acid, isoprenesulfonic acid, gluconic acid, lactic acid, citric acid, tartaric acid, malic acid, glycolic acid, malonic acid, formic acid, oxalic acid, succinic acid, fumaric acid, malefic acid and phthalic acid. Among these, gluconic acid, lactic acid, citric acid, tartaric acid, malic acid, glycolic acid, malonic acid, formic acid, oxalic acid, succinic acid, fumaric acid, malefic acid and phthalic acid are preferred. Among these, tartaric acid, malic acid, succinic acid and phthalic acid are particularly preferred. These organic acids may be used alone or in combinations of two or more. As inorganic acids there may be mentioned nitric acid, hydrochloric acid and sulfuric acid, and these inorganic acids may also be used alone or in combinations of two or more. Combinations of organic acids and inorganic acids may also be used. These acids can be used at 0.1-10 parts by weight and especially 1-8 parts by weight to 100 parts by weight of the aqueous dispersion composition. An acid content in the range of 0.1-10 parts by weight is preferred to give an aqueous dispersion composition with excellent dispersability and sufficient stability, as well as minimal etching and an increased polishing rate.
According to the present invention, a composition containing no surfactant is preferred from the standpoint of polishing performance, but a surfactant may be added for more even dispersion of the particles, particularly the polymer particles, in the aqueous dispersion composition. The surfactant is preferably only present in a small amount from the standpoint of polishing performance. The surfactant content is preferably not greater than 0.15 wt %, more preferably not greater than 0.1 wt %, even more preferably not greater than 0.05 wt %, and especially not greater than 0.01 wt %. The surfactant is used in the procedure for production of the aqueous dispersion containing the polymer particles, and it remains as an impurity in the polymer particles or the water or aqueous medium; however, a lower content thereof will give a polymer particle-containing aqueous dispersion with superior heat resistance, antistatic properties, color fastness, and the like.
The surfactant is preferably contained in the aqueous dispersion or CMP slurry at not greater than 0.05 part by weight and preferably not greater than 0.03 part by weight, with respect to 100 parts by weight of the polymer particles. It is more preferably not greater than 0.01 part by weight, and especially not greater than 0.025 part by weight. Such a composition will exhibit even better heat resistance, antistatic properties, color fastness, and the like.
By thus limiting the surfactant content to a small amount, it is possible to maintain the polishing performance while obtaining particles with excellent dispersability, so that faster polishing can be achieved without creating scratches in the polishing surfaces.
The surfactant used may be a cationic surfactant, anionic surfactant or nonionic surfactant. As cationic surfactants there may be mentioned aliphatic amines, aliphatic ammonium salts and the like. As anionic surfactants there may be mentioned carboxylic acid salts such as fatty acid soaps, alkylether carboxylic acid salts and the like; sulfonic acid salts such as alkylbenzenesulfonic acid salts, alkylnaphthalenesulfonic acid salts, xcex1-olefinsulfonic acid salts and the like; sulfuric acid ester salts such as higher alcohol sulfuric acid ester salts, alkylether sulfuric acid salts, polyoxyethylene alkylphenylethers and the like; phosphoric acid ester salts such as alkylphosphoric acid esters, and the like. As nonionic surfactants there may be mentioned ethers such as polyoxyethylene alkyl ethers; ether esters such as polyoxyethylene ethers of glycerin esters; and esters such as polyethyleneglycol fatty acid esters, glycerin esters, sorbitan esters, and the like.
According to the present invention, addition of an alkali metal hydroxide, ammonia, an inorganic alkali salt, an inorganic acid or an organic acid for adjustment of the pH can improve the dispersability and stability of the aqueous dispersion composition. Ammonia, inorganic alkali salts and inorganic acids are particularly preferred.
As alkali metal hydroxides there may be used sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide and the like. Sodium hydroxide and potassium hydroxide are particularly preferred among these. As inorganic acids there may be used nitric acid, sulfuric acid phosphoric acid or the like, and as organic acids there may be used formic acid, acetic acid, oxalic acid, malonic acid, succinic acid, benzoic acid or the like. Nitric acid and sulfuric acid are commonly used. Adjustment of the pH of the aqueous dispersion composition can improve the dispersability while also increasing the polishing rate, and the pH is preferably determined as appropriate in consideration of the electrochemical properties of the working surface, the dispersability and stability of the polymer particles and the polishing rate.
The working film subjected to chemical mechanical polishing according to the present invention may be a silicon oxide film, amorphous silicon film, polycrystalline silicon film, single-crystal silicon film, silicon nitride film, pure tungsten film, pure aluminum film or pure copper film, or an alloy film of tungsten, aluminum or copper with another metal, formed on a wafer during manufacture of a semiconductor device such as a VLSI or the like. The working film may also be an oxide or nitride film of a metal such as tantalum or titanium.
When the polishing surface of the working film on the wafer is a metal, the polishing rate can be vastly improved by adding an oxidizing agent to the aqueous dispersion composition. The oxidizing agent used may be appropriately selected by a Pourbaix diagram, for example, based on the electrochemical properties of the working surface.
The polymer particles contained in the aqueous dispersion used for chemical mechanical polishing of working films on wafers are preferably selected as appropriate depending on the hardness of the working film. For example, in the case of working films made of aluminum or the like having low hardness, it is preferred to use an aqueous dispersion containing polymer particles with a relatively low hardness. On the other hand, in the case of working films of high hardness such as tungsten, it is necessary to use an aqueous dispersion containing polymer particles of relatively high hardness provided by a high degree of crosslinking.
The chemical mechanical polishing of the working film on the wafer using the aqueous dispersion composition of the present invention can be accomplished with a commercially available chemical mechanical polishing device (such as Model xe2x80x9cLGP510xe2x80x9d or xe2x80x9cLGP552xe2x80x9d by Lapmaster SFT Corp.), which has been used in conventional methods employing metal oxide particles as abrasive particles.
After the polishing, it is preferred to remove the residual polymer particles remaining on the polishing surface. The particle removal can be accomplished by a common washing method, and the polishing surface can be heated at high temperature in the presence of oxygen to burn the polymer particles for their removal. As specific methods for burning there maybe mentioned exposure to oxygen plasma, or ashing treatment with plasma whereby oxygen radicals are supplied in a downflow; these allow the residual polymer particles to be easily removed from the polishing surface.
For polishing of a wafer working film that is a metal film in combination with a low-permittivity insulating film, the use of common inorganic particles such as silica or alumina can result in a faster polishing rate on the low-strength, low-permittivity insulating film which is not supposed to be polished, thus creating numerous scratches. In such cases, a process employing an aqueous dispersion composition according to the present invention can, as one of its features, lower the polishing rate and thus prevent scratches.
The manufacturing process of the present invention is a process for manufacture of semiconductor device using the CMP slurry specified above. Here, xe2x80x9csemiconductor devicexe2x80x9d is used in a wide sense to include polished wafers, various devices (including apparatus) provided with or bearing such wafers, plates manufactured from such wafers, and various devices (including apparatus) provided with such plates (i.e., devices on which such plates are mounted).
The present invention will now be explained in further detail by reference to certain examples which are provided solely for purposes of illustration and are not intended to be limitative.
(1) Preparation of aqueous dispersions of polymer particles